Immunohistochemical assessment of proliferation and apoptosis of keratinocytes after a single fractional ionizing irradiation

Radiation therapy for non-melanoma skin cancers is used by oncologists and radiologists in cases of ineffective surgical treatment and as adjuvant or palliative therapy. The creation of experimental models to study the proliferative-apoptotic balance of keratinocytes makes it possible to assess the degree and depth of post-radiation skin damage after exposure to electrons in order to select optimal doses in the clinic. The purpose of the study: immunohistochemical assessment of proliferation and apoptosis of keratinocytes after local electron irradiation of the skin. The experiment used male Wistar rats (n=50), which were divided into groups: I - control (n=20), which were injected with saline solution, and experimental rats, which received local electron irradiation of the skin of the outer surface of the thigh: II - 8 Gy (n=10; single), III - 40 Gy (n=10, single), IV - fractional 13 Gy for 6 days with a total focal dose of 78 Gy (n=10;). After completion of the experiment, a skin biopsy of the outer surface of the thigh was performed and an immunohistochemical study of histological preparations with antibodies to the Ki-67, caspase-3 and p53 antigens was performed. Analysis of skin fragments after irradiation showed a shift in the proliferative-apoptotic balance towards keratinocyte apoptosis: a decrease in the level of Ki-67 expression and an increase in the number of p53-positive cells. After a single irradiation with electrons at doses of 8 Gy and 40 Gy, a significant increase in keratinocytes stained positively with antibodies to caspase-3 was found - by 3.4 and 6.6 times, respectively, and with a fractional irradiation mode at a total dose of 78 Gy - by 11.6 times compared to the control group. Thus, local irradiation with electrons in single doses of 8 Gy and 40 Gy leads to a shift in the proliferative-apoptotic balance of keratinocytes towards their apoptosis, the activity of which is directly proportional to the dose of ionizing radiation, and the fractional mode (total focal dose of 78 Gy) leads to partial desquamation of the epithelium and inflammatory infiltration.